Higgs-to-Higgs Cascade
Dear Madgraph Team,
we are trying to generate cascade decays of BSM Higgs bosons in a singlet extension (called the TRSM, see 1908.08554). The model contains three CP-even scalars and we are interested in the p p -> h125 -> h1 h2 -> h1 h1 h1 decay chain, where h125 denotes the SM-like Higgs boson.
I generated a UFO for the model with Feynrules (can be found here https:/
import model TRSM
generate p p > h3 > h1 h2
launch
set mh1 20
set mh2 60
set decay 25 auto
set decay 35 auto
set decay 36 auto
(where h1=25, h2=35, h3=36 and mh3=125 by default) yielding a cxn of ~0.37. For this parameter point the BR(h2->h1 h1) is essentially 1 and madgraph correctly calculates it to be 9.999389e-1. Using madspin to do the decay
import model TRSM
generate p p > h3 > h1 h2
launch
madspin=ON
set mh1 20
set mh2 60
set decay 25 auto
set decay 35 auto
set decay 36 auto
set spinmode none
decay h2 > h1 h1
works as expected and gives essentially the identical cxn ~0.37. So far so good, if I instead use madgraph to do the decay
import model TRSM
generate p p > h3 > h1 h2, h2 > h1 h1
launch
set mh1 20
set mh2 60
set decay 25 auto
set decay 35 auto
set decay 36 auto
I get a cross section that is smaller by several orders of magnitude ~0.00078. I tried explicitly disabling cuts for h1 by setting {25: 0} = pt_min_pdg, cut_decays is False anyway, and massively increasing bwcutoff had no relevant impact on the result. Note that the width of both h3 and h2 is pretty small (few MeV), so the narrow width approximation should be very good.
I am lost to what is happening here, any help would be appreciated.
Thanks,
Jonas
Question information
- Language:
- English Edit question
- Status:
- Solved
- Assignee:
- No assignee Edit question
- Solved by:
- Olivier Mattelaer
- Solved:
- Last query:
- Last reply: